Approximately five to ten percent of patients with cystic fibrosis ar believed to have the disease because cells lining their airways are not capable of synthesizing a protein called the cystic fibrosis transmembrane conductance regulator due to premature stop mutations (CFTR). We have discovered that in some cases it may be possible to stimulate cells to make the normal protein by treating them with systemic administration of gentamicin designed to have maximal effects on the sweat test. The purpose of this study is to determine whether these same antibiotics might also help a subgroup of cystic fibrosis patients by allowing their lung cells to produce a normal CFTR protein. This project intends to provide the resources necessary to develop and complete a clinical trial of aminoglycoside antibiotics to 10 cystic fibrosis patients possessing the R553X, G542X,W1128X and R1162X mutations.